由诺贝尔物理学奖得主、英国曼彻斯特大学Kostya Novoselov教授领衔，与新加坡国立大学Daria Andreeva教授、中科院金属所任文才教授和北航单光存教授合作为FOP刊组织了专题“Graphene and other Two-Dimensional Materials”。这一专题涵盖2D材料的实验合成、实验表征（ARPES，STM，光学吸收等）、电学特性、电磁微波吸收特性、光学特性、磁学特性、拓扑特性及潜在应用等方面。文章已陆续上线，将分两部分刊载。

Special Collection: Graphene and other Two-Dimensional Materials (Part I)

(Eds. Daria Andreeva, Wencai Ren, Guangcun Shan & Kostya Novoselov)

REVIEW

The rise of two-dimensional MoS₂ for catalysis

Jun Mao (毛军), Yong Wang (王勇), Zhilong Zheng (郑智龙), and Dehui Deng (邓德会)*

Abstract: Two-dimensional (2D) MoS₂ is used as a catalyst or support and has received increased research interest because of its superior structural and electronic properties compared with those of bulk structures. In this article, we illustrate the active sites of 2D MoS₂ and various strategies for enhancing its intrinsic catalytic activity. The recent advances in the use of 2D MoS₂–based materials for applications such as conventional heterogeneous catalysis, electrocatalysis, and photocatalysis are discussed. We also discuss the future opportunities and challenges for 2D MoS₂–based materials, in both fundamental research and industrial applications.

REVIEW

Environmental engineering of transition metal dichalcogenide optoelectronics

Trevor LaMountain, Erik J. Lenferink, Yen-Jung Chen, Teodor K. Stanev, and Nathaniel P. Stern*

Abstract: The explosion of interest in two-dimensional van der Waals materials has been in many ways driven by their layered geometry. This feature makes possible numerous avenues for assembling and manipulating the optical and electronic properties of these materials. In the specific case of the monolayer transition metal dichalcogenide semiconductors, the direct band gap combined with the exibility for manipulation of layers has made this class of materials promising for optoelectronics. Here, we review the properties of these layered materials and the various means of engineering their properties for optoelectronics. We summarize approaches to control using their structural and chemical environment, and we give particular detail on the integration of these materials into engineered optical fields to control their optical characteristics. This combination of controllability from their layered surface structure and photonic environment provide an expansive landscape for novel optoelectronic phenomena.

REVIEW

Two-dimensional materials: Emerging toolkit for construction of ultrathin high-efficiency microwave shield and absorber

Mingjun Hu^*, Naibai Zhang, Guangcun Shan, Jiefeng Gao, Jinzhang Liu, and Robert K. Y. Li*

Abstract: Two-dimensional (2D) materials generally have unusual physical and chemical properties owing to the confined electro-strong interaction in a plane and can exhibit obvious anisotropy and a significant quantum-confinement effect, thus showing great promise in many fields. Some 2D materials, such as graphene and MXenes, have recently exhibited extraordinary electromagnetic-wave shielding and absorbing performance, which is attributed to their special electrical behavior, large specific surface area, and low mass density. Compared with traditional microwave attenuating materials, 2D materials have several obvious inherent advantages. First, similar to other nanomaterials, 2D materials have a very large specific surface area and can provide numerous interfaces for the enhanced interfacial polarization as well as the reflection and scattering of electromagnetic waves. Second, 2D materials have a particular 2D morphology with ultrasmall thickness, which is not only beneficial for the penetration and dissipation of electromagnetic waves through the 2D nanosheets, giving rise to multiple reflections and the dissipation of electromagnetic energy, but is also conducive to the design and fabrication of various well-defined structures, such as layer-by-layer assemblies, core–shell particles, and porous foam, for broadband attenuation of electromagnetic waves. Third, owing to their good processability, 2D materials can be integrated into various multifunctional composites for multimode attenuation of electromagnetic energy. In addition to behaving as microwave reflectors and absorbers, 2D materials can act as impedance regulators and provide structural support for good impedance matching and setup of the optimal structure. Numerous studies indicate that 2D materials are among the most promising microwave attenuation materials. In view of the rapid development and enormous advancement of 2D materials in shielding and absorbing electromagnetic wave, there is a strong need to summarize the recent research results in this field for presenting a comprehensive view and providing helpful suggestions for future development.

RESEARCH

Monolayered semiconducting GeAsSe and SnSbTe with ultrahigh hole mobility

Yu Guo, Nan Gao, Yizhen Bai, Jijun Zhao^*, and Xiao Cheng Zeng*

(Cover story)

Abstract: High carrier mobility and a direct semiconducting band gap are two key properties of materials for electronic device applications. Using first-principles calculations, we predict two types of two-dimensional semiconductors, ultrathin GeAsSe and SnSbTe nanosheets, with desirable electronic and optical properties. Both the GeAsSe and SnSbTe sheets are energetically favorable, with formation energies of −0.19 and −0.09 eV/atom, respectively, and have excellent dynamical and thermal stability, as determined by phonon dispersion calculations and Born–Oppenheimer molecular dynamics simulations. The relatively weak interlayer binding energies suggest that these monolayer sheets can be easily exfoliated from the bulk crystals. Importantly, monolayer GeAsSe and SnSbTe possess direct band gaps (2.56 and 1.96 eV, respectively) and superior hole mobility (～20 000 cm²×V⁻¹×s⁻¹), and both exhibit notable absorption in the visible region. A comparison of the band edge positions with the redox potentials of water reveals that layered GeAsSe and SnSbTe are potential photocatalysts for water splitting. These exceptional properties make layered GeAsSe and SnSbTe promising candidates for use in future high-speed electronic and optoelectronic devices.

RESEARCH

Interfacial charge transfer in WS₂ monolayer/CsPbBr₃ microplate heterostructure

Zhen-Zhong Yan, Zhao-Han Jiang, Jun-Peng Lu^*, and Zhen-Hua Ni

Abstract: Integration of heterogenous materials produces compelling physical phenomena and increased performance of optoelectronic devices. In this work, we integrate CsPbBr₃ microplate with WS₂ monolayer to investigate the interfacial carrier transfer mechanism in the heterojunction. The quenching of photoluminescence (PL) emission from CsPbBr₃ and WS₂ after heterostructure formation indicates efficient charge transfer in the junction. Low-temperature PL spectra reveal that the decreasing PL of WS₂ arises from the vanishing of biexcitons. Photodetection based on the WS₂/CsPbBr₃ heterostructure is demonstrated. The higher performance from the junction further certifies the occurrence of charge transfer in the heterojunction.

RESEARCH

Vertically aligned γ-AlOOH nanosheets on Al foils as flexible and reusable substrates for NH₃ adsorption

Chen Yang, Ying Chen^*, Dan Liu, Jinfeng Wang, Cheng Chen, Jiemin Wang, Ye Fan, Shaoming Huang, and Weiwei Lei^*

Abstract: Vertically aligned γ-AlOOH nanosheets (NSs) have been successfully fabricated on flexible Al foils via a solvothermal route without morphology-directing agents. Three different reaction temperatures (25, 80, and 120 °C) and reaction times (30 min, 45 min, and 24 h) are discussed for the growth period, which efficiently tune the density and size of the γ-AlOOH NSs. Meanwhile, the growth speed of the nanosheets confirms that dominant growth stage is seen in the initial 45min. Furthermore, the interlayer of the γ-AlOOH NSs displays an average height of 140 nm and superhydrophilicity. By dynamic adsorption, the as-synthesized γ-AlOOH NSs exhibit an outstanding NH₃ adsorption capacity of up to 146 mg/g and stably excellent regeneration for 5 cycles. The mechanism of NH₃ adsorption has been explained by the Lewis acid/base theory between NH₃ molecules and in-plane of γ-AlOOH NSs. The H-bond interactions among the NH₃ molecules and the edge groups (-OH) further improve the capture ability of the nanosheets.

全文下载：http://journal.hep.com.cn/fop/EN/collection/showCollection.do?id=191 

--------------------------------------------

Special Collection:  Graphene and other Two-Dimensional Materials (Part II)

(Eds. Daria Andreeva, Wencai Ren, Guangcun Shan & Kostya Novoselov)

(Coming soon)

PERSPECTIVE

Graphene and other two-dimensional materials 

Kostya Novoselov*, Daria Andreeva, Wencai Ren, and Guangcun Shan

REVIEW

The art of designing carbon allotropes

Run-Sen Zhang and Jin-Wu Jiang*

Abstract: As stimulated by the success of graphene and diamond, a variety of carbon allotropes have been discovered in recent years in either two-dimensional or three-dimensional configurations. These emerging new carbon allotropes have some quite different novel mechanical or physical properties, though they also share some common features. In this review, we comparatively survey some major properties for fifteen newly discovered carbon allotropes. By comparing their structural topology, we disclose a general routine to design most carbon allotropes from two mother structures – graphene and diamond. We also discuss several future prospects as well as the current challenges in designing new carbon allotropes.

REVIEW

Coulomb drag and exciton condensation in graphene double-layer heterostructures

Xiaomeng Liu, Jia Li, Cory dean, and Philip Kim*

Abstract: This review discusses effects and phenomena caused by interlayer interaction in graphene double-layer heterostructures, where two graphene layers are separated by a thin insulator. Two interaction-driven phenomena extensively studied in semiconductor double quantum wells, Coulomb drag and exciton condensation, are introduced. Under high magnetic fields and at low temperatures, exciton condensation was observed when electrons from two layers coherently fill one Landau level. We then focus on graphene double-layer systems and discuss the fabrication as well as the unique properties and capabilities of this new platform. Theoretical proposals and experimental attempts to realize exciton condensation in graphene double-layer under zero magnetic field are reviewed. In drag experiments, unconventional drag have been observed in monolayer graphene double-layer near charge neutrality and in bilayer graphene double-layer. Mechanisms that may cause these unconventional drag effects are examined. Under strong magnetic fields, the band structure of the graphene is flattened by Landau quantization. Study of exciton condensation in this regime is presented, with emphasis on unique observations enabled by the highly tunable and strongly interacting graphene double-layer platform. Finally, we briefly discuss open questions and prospective research directions in graphene and other 2D material double-layer systems.

REVIEW

Graphene based functional devices: A short review 
Rong Wang, Xingang Ren, Ze Yan, Wei E.I. Sha, Li Jun Jiang*, and Guangcun Shan*

Abstract: Graphene is an ideal 2D material system bridging electronic and photonic devices. It also breaks the fundamental limits of electronics and photonics named speed and size, respectively. Graphene offers multiple functions of signal emission, transmission, modulation, and detection in a broad band, high speed, compact size, and low loss. Here, we will have a bird’s eye view of the graphene based functional devices at microwave, terahertz, and optical frequencies. The basic physical foundation and computational model will be discussed as well.

RESEARCH

Probing interlayer interactions in wse₂-graphene heterostructures by ultralow frequency Raman spectroscopy

Yue Liu (刘月), Hao Zhang (张昊), Yu Zhou (周煜), Feirong Ran (冉飞荣), Weihao Zhao (赵炜昊), Lin Wang (王琳), Jindong Zhang (张锦东), Xiao Huang (黄晓)*, Hai Li (李海) 

Abstract: Interlayer interactions at heterointerfaces of van der Waals heterostructures (vdWHs), which consist of vertically stacked two-dimensional (2D) materials, play important roles in determining their properties. The interlayer interactions are tunable from non-coupling to strong coupling by controlling the twist angle and distance between adjacent layers. However, the influence of stacking sequence and individual component thickness on the properties of vdWHs is rarely explored. In this work, the influence of stacking sequence of WSe₂ and graphene in vdWHs of graphene-on-WSe₂ (graphene/WSe₂) or WSe₂-on-graphene (WSe₂/graphene), as well as their thickness on their interlayer interaction was systematically investigated by ultralow frequency (ULF) Raman spectroscopy. A series of ULF breathing modes of WSe₂ nanosheets in these vdWHs were observed with frequencies highly dependent on graphene thickness. Interestingly, the ULF breathing modes of WSe₂ red shifted in both graphene/WSe₂ and WSe₂/graphene configurations, and the amount of shift in the former is much larger than that in the latter. In contrast, no obvious ULF shift was observed by varying the twist angle between WSe₂ and graphene. This indicates that the interlayer interaction is more sensitive to the stacking sequence compared with the twist angle. Our results provide alternative approaches to modulate the interlayer interaction of vdWHs and thus tune their optical and optoelectronic properties.

REVIEW

Two-dimensional materials-based optical modulators

Xuetao Gan and Dirk Englund, et al.

(Coming soon)